362 Transactions of the Society. 



in many parts of this country, with conspicuous orange phis- 

 modium that feeds on leathery fungi, and is easily cultivated 

 indoors ; the grape-like clusters of small iridescent grey sporangia 

 may be found in favourable seasons, from the summer on into 

 winter, hanging in quantities from the sides <>f fungus-grown logs 

 in sheltered situations. At the least touch the membranous 

 sporangium-walls break and a shower of dark spores is shed, to be 

 carried away on the breeze, or to be washed down by rain. The 

 spores are not, however, all shed at once, for their dispersion is 

 checked or regulated to some extent by the " capillitium," a 

 structure which in this species consists of a delicate network of 

 tubules, stiffened with deposits of carbonate of lime, and attached 

 to the sporangium-walls. "When a ripe spore is moistened, the 

 contents swell, burst the spore-wall, and emerge as a uninucleated 

 swarm-spore or zoospore. This at first creeps about in an amoeboid 

 manner, but soon acquires a flagellum and swims. From the 

 opposite end of the cell to the flagellum pseudopodia are extended, 

 to which bacteria and other food particles adhere, to be conveyed 

 into the interior of the cell and dissolved in digestive vacuoles. 

 After feeding for some time, the swarm-cell divides, its nucleus 

 meanwhile undergoing mitotic division. This process may be 

 repeated several times. Dr. Jahn has proved that these swarm- 

 cells are to be regarded as gametes ; they fuse in pairs, their 

 nuclei unite, and zygotes are formed which grow into plasmodia.* 

 The process of fusion was not actually observed, but his cultiva- 

 tions showed numbers of zygotes with large single nuclei, in which 

 when mitosis occurred he could count sixteen chromosomes, whereas 

 the number of chromosomes in the swarm-cell nucleus is eiglit. 

 The zygotes could often be distinguished at a glance l)y their lialjit 

 of absorbing the gametes and devouring them in digestive vacuoles 

 (PI. XI, figs. 2, 3), while the gametes feed only on minute organisms, 

 such as bacteria. The plasmodia, as the zygotes are termed when 

 they begin to absorb food, increase in size also by uniting witli one 

 another. Within their substance a continual rhythmic streaming 

 of granular protoplasm is set up, by means of which all parts are 

 kept in comniTinication. The plasmodium spreads out in a net- 

 work of veins, searching for food, and grows rapidly; the nuclei 

 meanwhile divide pari passu. Several times they have been seen 

 to divide by mitosis simultaneously over a wide extent of plas- 

 modium ; considering the many prolonged and unsuccessful 

 attempts that have been made to observe this process, it seems not 

 improbable that they also sometimes divide by direct division. 

 After a time, the length of which varies according to the amount 

 of the food supply, or also, as Dr. Jahn has observed, as the result 

 of cold, the Plasmodium concentrates at numerous points to form 



* E. Jahn (1911), Myxomycetenstudien. 8. Der Sexualakt. Ber. Deutsch. Bot. 

 Ges., xxix. p. 2.31. 



